DRX handling in LTE license assisted access operation

ABSTRACT

Methods and structures are disclosed which facilitate handling discontinuous reception (DRX) in Long Term Evolution (LTE) type communication signal reception and transmission using one carrier, such as a licensed carrier, and another carrier, such as an unlicensed carrier, in the presence of other transmissions using the other carrier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 62/146,213, filed Apr. 10, 2015 and is acontinuation of U.S. application Ser. No. 15/073,135, filed Mar. 17,2016, which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The following disclosure relates to wireless telecommunicationtransmissions using an unlicensed carrier, and particularly relates toapproaches for handling discontinuous reception (DRX) in Long TermEvolution (LTE) type communication signal reception and transmissionusing one carrier, such as a licensed carrier, and another carrier, suchas an unlicensed carrier, in the presence of other transmissions usingthe other carrier.

BACKGROUND

LTE Advanced is being considered for deployment in the unlicensedspectrum in the 5 GHz band. To do so, licensed spectrum (e.g., in therange 400 MHz to 3.8 GHz) and spectrum in unlicensed spectrum bandswould be aggregated together in the same way that the licensed spectrumbands are treated in standard LTE Advanced carrier aggregation (CA).Regulatory authorities around the world have defined or are defining awide variety of requirements so that various systems can inter-operateor coexist with incumbent users in the unlicensed bands, notablyincluding WiFi deployments.

For LTE Advanced (LTE Release 10-12) carrier aggregation (CA) or DualConnectivity, an eNB (E-UTRAN Node B or “evolved Node-B”) may be used.An eNB is connected to a mobile phone network that communicates withmobile handsets (i.e., “user equipment” or UEs) and that configures asecondary serving cell (Scell) to the UE to provide additional frequencyresources (i.e., a secondary carrier or a secondary component carrier(CC)) for communication in addition to the primary serving cell (Pcell).The Scell is typically activated for a UE at the onset of a data bursttransmission for the UE and deactivated after the transmission iscomplete. Activation is done by using an activation command MAC layercontrol element (MAC CE). Deactivation is done either upon expiry of adeactivation timer or by using an explicit deactivation command MAC CE.Additionally, a UE operating in an Advanced LTE (LTE Release 12) networkcan expect at least discovery signals from the eNB on the Scell carrierwhile the carrier is deactivated. After receiving an activation commandfor the Scell, the UE expects cell specific reference signal (CRS)transmissions from the eNB on the Scell carrier beginning during thesubframe in which the activation command is received until the subframein which the Scell is deactivated.

For further Advanced LTE (LTE Release 13) Scell, operation on unlicensedcarriers continues to be studied. The initial focus of the studies isScell operation via a CA mechanism. However, it has been perceived thatsome of the procedures identified for CA can also be reused for dualconnectivity (i.e., when the Scell and Pcell belong to different cellgroups).

Due to regulatory requirements, and due to the need to for LTE Advancedto co-exist with other wireless systems (e.g., Wi-Fi), LTE devices(i.e., UEs and eNBs) need to take several issues into account whileoperating on an unlicensed carrier frequency (i.e., using LicenseAssisted Access LTE, or “LAA LTE”).

First, before transmitting on an unlicensed carrier, the LTE devices(e.g., eNB) typically have to check whether the carrier (i.e., thecarrier frequency) is busy using some form of ‘listen before talk’ (LBT)mechanism, then an LTE device can begin transmissions only if thecarrier is free. LBT typically includes measuring the energy on thecarrier (sometimes referred to as sensing) for a short duration (e.g., 9us or 20 us) and determining whether the measured energy is less than athreshold (e.g., −82 dBm or −62 dBm). If the energy is less than thethreshold, the carrier is determined to be free. Some examples of LBTinclude the CCA-ED (clear channel assessment-energy detect) and CCA-CS(clear channel assessment-carrier sense) mechanisms defined in IEEE802.11 specifications, and CCA mechanisms specified in ETSI EN 301 893specification.

Second, transmissions on the carrier typically also have to followdiscontinuous transmission requirements (DCT requirements), i.e., theLTE device can continuously transmit for only Xms (e.g., X=4 ms as perregulations for some regions, and up to 13 ms per regulations for otherregions), after which it has to cease transmission for some duration(sometimes referred to as the idle period), then perform LBT, andreinitiate transmission only if the LBT procedure is successful (i.e.,the LBT procedure indicates that the carrier is not busy). The devicemay perform LBT towards the end of the idle period.

As a result, mechanisms are needed to enable more efficient wirelessnetwork operation in both the licensed and unlicensed carrier spectrums.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings in which:

FIG. 1 illustrates a communications system in accordance with variousinvention embodiments;

FIG. 2 illustrates a possible configuration of a computing system to actas a base station;

FIG. 3 is a block diagram of an embodiment of a telecommunicationapparatus or electronic device that operates as a User Equipment (UE);

FIG. 4 illustrates a discontinuous reception (DRX) cycle used to savepower in LTE communications;

FIG. 5A illustrates normal operation with an Scell on a licensedcarrier;

FIG. 5B illustrates Scell operation using an unlicensed network wherethe eNB is unable to transmit packets via the Scell before the end ofthe DRX active time;

FIG. 6 illustrates operation of an embodiment in which the DRX activetime is extended due to failure of a clear channel assessment performedat the UE; and

FIG. 7 illustrates operation of an embodiment in which the DRX activetime is extended based upon a network command or order.

DETAILED DESCRIPTION

Embodiments will now be described more fully hereinafter with referenceto the accompanying drawings, in which various embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey pertinent aspects of the invention to those skilled in the art.

As will be explained and discussed in more detail below, variousembodiments provide enhancements or modifications to the creation andreception of LTE signals and channels in order to enable improvedoperation in both licensed and unlicensed frequency spectrums.

In one embodiment, a method in a mobile device for communicating datapackets with a first cell operating on an unlicensed carrier isprovided. In some embodiments, the method includes: monitoring, in themobile device, for a signal addressed to the mobile device from thefirst cell during an active time having an initial duration equal to aninitial active time; extending, in the mobile device, the active time inresponse to a determination that the unlicensed carrier is occupiedduring at least a portion of the initial active time; and communicatinga data packet between the mobile device and the first cell during theextended active time when the unlicensed carrier is not otherwiseoccupied.

In some embodiments, the communicating a data packet between the mobiledevice and the first cell includes: receiving, from the first cell, acontrol channel indicating a transmission of a data channel to themobile device; and decoding, in the mobile device, the data packet fromthe data channel.

In some embodiments, the communicating a data packet between the mobiledevice and the first cell includes: receiving, from the first cell, acontrol channel indicating resources for transmission of a data packetby the mobile device; and transmitting the data packet using theindicated resources.

In some embodiments, the method also includes further extending, in themobile device, the extended active time in response to a determinationthat the unlicensed carrier is occupied during at least a portion of theextended active time subsequent to the initial active time.

In some embodiments, the determination that the unlicensed carrier isoccupied is based upon a clear channel assessment (CCA), performed inthe mobile device, that the unlicensed carrier is occupied, and thecommunicating a data packet between the mobile device and the first cellcomprises receiving the data packet from the first cell. In someembodiments the CCA performed in the mobile device utilizes a CCAthreshold that is more aggressive than a CCA threshold utilized by thefirst cell to perform a corresponding CCA at substantially the sametime.

In some embodiments, the method also includes: determining whether theunlicensed carrier is occupied at or prior to each subframe in theinitial active time; and extending the active time by one subframe foreach subframe of the initial active time during which the unlicensedcarrier is occupied.

In some embodiments, the extended active time is applied to operationwith all configured cells for the mobile device. In some embodiments,the extended active time is applied only to operation with the firstcell.

In some embodiments, the determination that the unlicensed carrier isoccupied comprises receiving, by the mobile device, a command to extendthe active time based upon a determination at the first cell that theunlicensed carrier is occupied. In some embodiments, the command isreceived from a second cell operating on a licensed carrier. In someembodiments, the command is received from the first cell on theunlicensed carrier. In some embodiments, the communicating a data packetbetween the mobile device and the first cell comprises transmitting thedata packet to the first cell in response to receiving a signaladdressed to the mobile device from the first cell during the extendedactive time. In some embodiments, the communicating a data packetbetween the mobile device and the first cell comprises receiving thedata packet from the first cell in response to receiving a signaladdressed to the mobile device from the first cell during the extendedactive time. In some embodiments, the method further includes extendingthe active time based upon transmission burst configuration signalingreceived from a base station.

In some embodiments, the method further includes placing at leastportions of the mobile device in a reduced power mode at times otherthan the active time, wherein the active time comprises a discontinuousreception (DRX) active time.

In another method embodiment, a method in a base station forcommunicating data with a mobile device using an unlicensed carrier isprovided. In some embodiments, the method includes: configuring themobile device with a first cell on an unlicensed carrier and a secondcell on a licensed carrier; determining whether the unlicensed carrieris occupied during an active time for the mobile device, the active timehaving an initial duration equal to an initial active time;transmitting, in response to determining that the unlicensed carrier isoccupied during at least a portion of the initial active time, a commandto the mobile device to extend the active time; and then communicating,during the extended active time, a data packet between the mobile deviceand the first cell when the unlicensed carrier is not otherwiseoccupied.

In some embodiments, the method further includes transmitting, inresponse to determining that the unlicensed carrier is occupied duringat least a portion of the extended active time subsequent to the initialactive time, a command to the mobile device to further extend the activetime.

In some embodiments, the determining that the unlicensed carrier isoccupied is based upon a clear channel assessment (CCA), performed inthe first cell, that the unlicensed carrier is occupied, and thecommunicating a data packet between the mobile device and the first cellcomprises transmitting the data packet from the first cell to the mobiledevice. In some embodiments, the CCA performed in the first cellutilizes a CCA threshold that is less aggressive than a CCA thresholdutilized by the mobile device to perform a corresponding CCA atsubstantially the same time.

In some embodiments, the method further includes: determining whetherthe unlicensed carrier is occupied at or prior to each subframe in theinitial active time; and extending the active time by one subframe foreach subframe of the initial active time during which the unlicensedcarrier is occupied.

In some embodiments, the transmitting, in response to determining thatthe unlicensed carrier is occupied during at least a portion of theinitial active time, a command to all mobile devices configured for thefirst cell, to extend the respective active time for each such mobiledevice.

In some embodiments, the command includes an indicated number ofsubframes to extend the active time. In some embodiments, the command istransmitted to the mobile device from the second cell on the licensedcarrier. In some embodiments, the command is transmitted to the mobiledevice from the first cell on the unlicensed carrier. In someembodiments, the communicating a data packet between the mobile deviceand the first cell comprises receiving the data packet from the mobiledevice.

In an apparatus embodiment, a mobile device for communicating datapackets with a first cell operating on an unlicensed carrier isprovided. In some embodiments, the mobile device includes a transceiver,and a processor coupled to the transceiver. The mobile device isoperable to: monitor for a signal addressed to the mobile device fromthe first cell during an active time having an initial duration equal toan initial active time; extend the active time in response to adetermination that the unlicensed carrier is occupied during at least aportion of the initial active time; and communicate, in response toreceiving a signal addressed to the mobile device from the first cellduring the extended active time, a data packet between the mobile deviceand the first cell when the unlicensed carrier is not otherwiseoccupied.

In some embodiments, the mobile device is operable to further extend theextended active time in response to a determination that the unlicensedcarrier is occupied during at least a portion of the extended activetime subsequent to the initial active time.

In some embodiments, the determination that the unlicensed carrier isoccupied is based upon a clear channel assessment (CCA), performed inthe mobile device, that the unlicensed carrier is occupied. In someembodiments, the CCA performed in the mobile device utilizes a CCAthreshold that is more aggressive than a CCA threshold utilized by thefirst cell to perform a corresponding CCA at substantially the sametime.

In some embodiments, the mobile device is operable to determine whetherthe unlicensed carrier is occupied at or prior to each subframe in theinitial active time, and extend the active time by one subframe for eachsubframe of the initial active time during which the unlicensed carrieris occupied.

In some embodiments, the determination that the unlicensed carrier isoccupied comprises receiving, by the mobile device, a command to extendthe active time based upon a determination at the first cell that theunlicensed carrier is occupied. In some embodiments, the data packetcommunicated between the mobile device and the first cell is receivedfrom the first cell.

In some embodiments, the mobile device is operable to place at leastportions of the mobile device in a reduced power mode at times otherthan the active time, wherein the active time comprises a discontinuousreception (DRX) active time.

In another apparatus embodiment, a base station for communicating datawith a mobile device using an unlicensed carrier is provided. In someembodiments, the base station includes a transceiver, and a processorcoupled to the transceiver. The base station is operable to: configurethe mobile device with a first cell on an unlicensed carrier and asecond cell on a licensed carrier; determine whether the unlicensedcarrier is occupied during an active time for the mobile device, theactive time having an initial duration equal to an initial active time;transmit, in response to determining that the unlicensed carrier isoccupied during at least a portion of the initial active time, a commandto the mobile device to extend the active time; and then communicate,during the extended active time, a data packet between the mobile deviceand the first cell when the unlicensed carrier is not otherwiseoccupied.

In another method embodiment, a method in a mobile device for receivingdata from a first cell operating on an unlicensed carrier is provided.In some embodiments, the method includes: monitoring, in the mobiledevice, for a signal addressed to the mobile device during a firstactive time; determining, in the mobile device, that the channel isoccupied during at least a portion of the first active time; monitoring,in the mobile device, for a signal addressed to the mobile device for anactive time extension period subsequent to the first active time, inresponse to determining that the channel is occupied; and receiving, inthe mobile device, data from the first cell during the active timeextension period.

In some embodiments, the determining that the channel is occupiedincludes determining that the channel is occupied based on a clearchannel assessment.

In some embodiments, the first active time is a minimum duration of timefor monitoring for a control channel.

In some embodiments, the determining whether the channel is occupiedcomprises determining whether the channel is occupied at or prior toeach subframe in the first active time, and the active time extensionperiod is incremented by one subframe for each subframe of the firstactive time for which the channel is occupied.

In some embodiments, the active time extension period is applied tooperation with all configured cells. In some embodiments, the activetime extension period is applied only to operation with the first cell.

In another method embodiment, a method in a mobile device for receivingdata from a first cell operating on an unlicensed carrier is provided.In some embodiments, the method includes: configuring a first cell on anunlicensed carrier and a second cell on a licensed carrier; monitoring,in the mobile device, for a first active time, for a signal addressed tothe mobile device from the second cell; receiving, in the mobile device,a message on the second cell indicating an extension of active time byan extension duration; monitoring, in the mobile device, for theextension duration subsequent to the first active time, for a signaladdressed to the mobile device from the second cell; and receiving, inthe mobile device, data from the first cell during the extensionduration.

In another method embodiment, a method for transmitting data to a mobiledevice using unlicensed spectrum is provided. In some embodiments, themethod includes: configuring the mobile device with a first cell on anunlicensed carrier and a second cell on a licensed carrier; performing aclear channel assessment of the unlicensed carrier during a first activeduration of the mobile device; determining whether the unlicensedcarrier is occupied during at least a portion of the first activeduration; transmitting, in response to determining that the unlicensedcarrier is occupied during at least a portion of the first activeduration, a message to the mobile device via the second cell indicatingan extension of the first active time by an extension period; and thentransmitting data to the mobile device via the first cell during theextension period.

FIG. 1 illustrates a communication system 100 including a network 102, abase station 104, such as an eNB, and a user equipment (UE) 106. Thebase station may also be referred to as a base unit, an access point(AP), access terminal (AT), Node-B (NB), enhanced Node-B (eNB), relaynode, home eNB, pico eNB, femto eNB or by other present or futureterminology used in the art for a base station derivation. Variouscommunication devices may exchange data or information through thenetwork 102. The network 102 may be an evolved universal terrestrialradio access (E-UTRA) or other type of telecommunication network. Anetwork entity, such as the base station 104, may assign a UE identifier(UEID) to the UE 106 when the UE 106 first joins the network 102. Forone embodiment, the base station 104 may be a distributed set of serversin the network 102. The UE 106 may be one of several types of handheldor mobile communication devices, such as, a mobile phone, a laptop, or apersonal digital assistant (PDA). In one embodiment, the UE 106 may be awireless local area network capable device, a wireless wide area networkcapable device, or any other wireless (i.e., mobile) device.

FIG. 2 illustrates a possible configuration of a computing system to actas the base station 104. The base station 104 may include aprocessor/controller 210, a memory 220, a database interface 230, atransceiver 240, input/output (I/O) device interface 250, and a networkinterface 260, connected through bus 270. The base station 104 mayimplement any operating system, such as Microsoft Windows®, UNIX, orLINUX, for example. Client and server software may be written in anyprogramming language, such as C, C++, Java or Visual Basic, for example.The server software may run on an application framework, such as, forexample, a Java® server or .NET® framework.

The controller/processor 210 may be any programmable processor. Variousembodiments of the disclosure may also be implemented or partiallyimplemented on a general-purpose or a special purpose computer, aprogrammed microprocessor or microcontroller, peripheral integratedcircuit elements, an application-specific integrated circuit or otherintegrated circuits, hardware/electronic logic circuits, such as adiscrete element circuit, a programmable logic device, such as aprogrammable logic array, field programmable gate-array, or the like. Ingeneral, any device or devices capable of implementing the decisionsupport method as described herein may be used to implement the decisionsupport system functions of this disclosure.

The memory 220 may include volatile and nonvolatile data storage,including one or more electrical, magnetic or optical memories such as arandom access memory (RAM), cache, hard drive, or other memory device.The memory may have a cache to speed access to specific data. The memory220 may also be connected to a compact disc-read only memory (CD-ROM),digital video disc-read only memory (DVD-ROM), DVD read write input,tape drive, solid state drive or other removable memory device thatallows media content to be directly uploaded into the system. Data maybe stored in the memory 220 or in a separate database (not specificallyshown). The database interface 230 may be used by thecontroller/processor 210 to access the database. The database maycontain any formatting data to connect the UE 106 to the network 102.The transceiver 240 may create a data connection with the UE 106. Thetransceiver 240 may configure a Physical Downlink Control Channel(PDCCH) and a Physical Uplink Control Channel (PUCCH) between the basestation 104 and the UE 106.

The I/O device interface 250 may be connected to one or more inputdevices that may include a keyboard, mouse, pen-operated touch screen ormonitor, voice-recognition device, or any other device that acceptsinput. The I/O device interface 250 may also be connected to one or moreoutput devices, such as a monitor, printer, disk drive, speakers, or anyother device provided to output data. The I/O device interface 250 mayreceive a data task or connection criteria from a network administrator.

The network connection interface 260 may be connected to a communicationdevice, modem, network interface card, a transceiver, or any otherdevice capable of transmitting and receiving signals from the network106. The network connection interface 260 may be used to connect aclient device to a network. The components of the base station 104 maybe connected via an electrical bus 270, for example, or linkedwirelessly.

Client software and databases may be accessed by thecontroller/processor 210 from memory 220, and may include, for example,database applications, word processing applications, as well ascomponents that embody the decision support functionality of the presentdisclosure. The base station 104 may implement any operating system,such as Microsoft Windows®, LINUX, or UNIX, for example. Client andserver software may be written in any programming language, such as C,C++, Java, or Visual Basic, for example. Although not required, thedisclosure is described, at least in part, in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by the electronic device, such as a general purpose computer.Generally, program modules include routine programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types. Moreover, those skilled in theart will appreciate that other embodiments of the disclosure may bepracticed in network computing environments with many types of computersystem configurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike.

FIG. 3 illustrates in a block diagram of one embodiment of atelecommunication apparatus or electronic device to act as the UE 106.The UE 106 may be capable of accessing the information or data stored inthe network 102. For some embodiments of the disclosure, the UE 106 mayalso support one or more applications for performing variouscommunications with the network 102. The UE 106 may be a handhelddevice, such as, a mobile phone, a laptop, a personal digital assistant(PDA) smart phone or other multi-function communication device. For someembodiments, the UE 106 may be a WiFi capable device, which may be usedto access the network 102 for data or by voice using VOIP and WiFicarrier frequency spectrums.

The UE 106 may include a transceiver 302, which is capable of sendingand receiving data over the network 102. The UE 106 may include aprocessor 304 that executes stored programs or applications that may,among other things, monitor, control and interact with the othercomponents of the UE 106. The UE 106 may also include a volatile memory306 and a non-volatile memory 308 which are used by the processor 304.The UE 106 may include a user interface 310 that may comprise user inputelements such as a keypad, display, touch screen, and the like. The userinterface 310 may also include user output elements that may comprise adisplay screen and/or vibration and illumination indicators. The UE 106may also include an audio interface 312 that may comprise elements suchas a microphone, earphone, and speaker. The UE 106 also may include acomponent interface 314 to which additional elements may be attached,for example, a universal serial bus (USB) interface. The UE 106 mayinclude a power supply 316. In addition, the UE 106 may be incorporatedas a peripheral or integral part of a larger system such as atransportation vehicle, building, entertainment center, kiosk, or gamingdevice, to name a few.

In Long Term Evolution (LTE) communication systems, physical layersignals and channels (e.g., a control channel like a physical downlinkcontrol channel (PDCCH), enhanced physical downlink control channel(EPDCCH); a data channel like a physical downlink shared channel(PDSCH); reference and synchronization signals like a primarysynchronization signal (PSS), secondary synchronization signal (SSS),cell-specific reference signal (CRS), channel state informationreference signal (CSI-RS), and discovery signals) are transmitted by abase station 104 using orthogonal frequency-division multiplexed (OFDM)symbols. For normal cyclic prefix (CP) operation, the OFDM symbols areof ˜71 us in duration. Seven OFDM symbols may comprise a 0.5 ms slot andtwo slots may comprise a 1 ms LTE subframe. Therefore, an example of anLTE subframe comprises 14 OFDM symbols. The PDCCH carries resourceassignment information for UEs, which is usually contained in thedownlink control information (DCI) message. Multiple PDCCHs can betransmitted in a same subframe using Control Channel Elements (CCE),each of which can be nine sets of four resource elements known asResource Element Groups (REG), which may be distributed across the first1 to 3 symbols of a subframe or slot within a subframe. For the uplink,Single Carrier Frequency Division Multiple Access (SC-FDMA) or DiscreteFourier Transform Spread OFDM (DFT-SOFDM) is used and the subframeduration is similar to downlink (i.e. 1 ms) and a subframe contains 14DFT-SOFDM symbols (or referred to as 14 OFDM symbols for brevity). Theuplink data and/or control is carried on the physical uplink sharedchannel (PUSCH). Other channels for uplink transmissions include thephysical uplink control channel (PUCCH), physical random access channel(PRACH), and uplink signals include sounding reference symbol (SRS) anduplink demodulation reference signal (DMRS) for demodulating uplinkchannels.

DRX Handling Issues

As mentioned above, license assisted access to unlicensed spectrum usingLTE (LAA-LTE) is being studied in the 3rd Generation Partnership Project(3GPP) as a potential extension of Carrier Aggregation. Compared toconventional LTE in licensed bands, the LAA operation has some specificrequirements related to operation in unlicensed bands. The requirementsimpose some operational differences at both the eNB and the UE incomparison to conventional LTE operation.

Also as mentioned above, LTE devices (i.e., UEs and eNBs) operating onan unlicensed carrier frequency must co-exist with other wirelesssystems (e.g., Wi-Fi). Thus, an LTE device typically has to checkwhether the carrier (i.e., the carrier frequency) is busy using someform of ‘listen before talk’ (LBT) mechanism, then the LTE device canbegin transmissions only if the carrier is free. In addition, the LTEdevice can continuously transmit for only a certain duration, afterwhich it has to cease transmission for an idle period, perform anotherLBT, and then reinitiate transmission only if LBT is successful. LBT canbe performed using a carrier sense or energy detect mechanism such asClear Channel Assessment (CCA). LBT and CCA are used interchangeably inthis disclosure.

Discontinuous Reception (DRX) is a feature that allows for UE batterysavings, by reducing the time periods when the UE actively monitors fora control channel transmitted by the eNB. A DRX cycle refers to arepeating sequence of subframes in which the UE monitors for a controlchannel in the early part of the sequence and then “sleeps” or “goesinto DRX” during the remaining part of the sequence. Referring now toFIG. 4, the DRX On-Duration 402 is the minimum number of subframes atthe start of the DRX cycle 404 that the UE is expected to monitor for acontrol channel addressed to the UE for possible allocations. The DRXActive Time refers to the total duration that a UE is awake and monitorsfor a control channel addressed to the UE. The active time initially hasthe same duration as the DRX On-Duration (and may be referred to hereinas the “initial active time”), but the active time may be extendedbeyond the end of the DRX On-Duration to include portions of the DRXopportunity time 406 (which may be referred to herein as the “extendedactive time” or “active time extension”). When the UE detects a controlchannel, the active time may be extended to allow for further packettransmission or retransmissions of packets. In such cases, the DRXactive time is therefore longer than the DRX On-Duration. The activetime includes both the initial active time and the extended active time.

The eNB can configure a UE to operate in DRX, wherein a UE is allowed towake at particular time durations (e.g., UE wakes up for a 5 ms durationevery 640 ms) to listen/receive signals/commands from the network. Ifthe UE receives a control channel during the 5 ms duration (whichcontrol channel may indicate that the UE should receive a data packettransmission), the UE continues to monitor the channel for data packets.The UE can continue to monitor the channel for additional data packetsuntil the UE does not receive a control channel for an inactivity timeduration. Conversely, if the UE does not receive a control channelduring the 5 ms duration, the UE may save battery by turning off itsreceiver functions for the remaining portion of the DRX cycle.

Consider, as an example, a conventional carrier aggregation operationwith a Pcell on carrier-1 and a Scell on carrier-2. When scheduling theUE, the MAC layer in the eNB treats the packets on the two carriersindependently. Specifically, the UE maintains separate HARQ (HybridAutomatic Repeat Request, also known as Hybrid ARQ) entities for eachcarrier, each controlling multiple HARQ processes. All HARQ transmissionand retransmission attempts of a given packet are performed through oneHARQ process; as a result, if a HARQ transmission attempt fails on onecarrier, the eNB does not perform a HARQ retransmission of the samepacket on a different carrier (i.e., channels). Given the use of twoindependent HARQ entities, there is an implicit partitioning of the datato be transmitted to the UE into two streams: one for transmission viathe Pcell and the other for transmission via the Scell. The eNBscheduler takes into account channel state information feedback andother measurement information to determine the relative sizes of the twostreams, while trying to ensure that the packets to be transmitted viathe Pcell and the Scell can be transmitted within the DRX On-Durationwith a high likelihood. That is, the eNB scheduler allocates data fortransmission via the two cells based on a certain number of subframesduring which it expects that the UE can be scheduled. The same analysiswould hold for the case of carrier aggregation with more than 2 cells,including up to 32 or 64 carriers. Examples of such channel stateinformation feedback include Channel Quality Indicator (CQI), PrecodingMatrix Indicator (PMI), and Rank indicator (RI). Examples of such othermeasurement information include Reference Signal Receive Power (RSRP),Reference Signal Receive Quality (RSRQ), and channel measurements basedon sounding reference signal.

FIG. 5A illustrates the operation with the Scell on a licensed carrieras described above. The data packets 502 to be transmitted to the UE arepartitioned by the eNB into data stream 504 for transmission via thePcell, and data stream 506 for transmission via the Scell. The Scell maybe associated with the same eNB as the Pcell, or may be associated witha different eNB. When the UE receives a packet from the Scell (e.g.,packet 510) or successfully decodes a control channel (e.g., for a firsttransmission) from the Scell, it extends the active time 512 inexpectation of additional imminent packets from the same Scell. Asshown, the active time 512 is longer than the DRX On-Duration 508. Sincethe eNB controls the allocation of channel resources for both the Pcelland Scell, the packets 506 are successfully transmitted by the Scell tothe UE.

However, if the Scell is operated on an LAA-LTE carrier (e.g., anunlicensed carrier) instead of a licensed carrier, there is also therequirement of successful Clear Channel Assessment (CCA) at the Scellbefore there can be a transmission to the UE (i.e., eNB performs a CCAto determine if the channel is free and then transmits data to the UEwhen the channel is free), and also discontinuous transmissionrequirements with limits on maximum channel occupancy time and idleperiods to cease transmission before performing another CCA. This canmake the partitioning into the first stream 504 and the second stream506 difficult (e.g., at the eNB), since the eNB scheduler does not havea guaranteed or a deterministic number of subframes that it can expectto be able to schedule on the Scell.

These issues lead to the following problems. First, depending on thechannel activity (e.g., other devices that are operating on theunlicensed carrier), the Scell may not be able to drain its bufferquickly. Also, due to there being fewer than the number of expectedsubframes for scheduling, the DRX active time at the UE could belengthened, but such would result in increased power requirements.Finally, the On-Duration timer may expire before the Scell drains itsbuffer, which results in (a) significantly delayed packets, and (b) theScell having to store the packets for transmission in the next DRXactive time.

FIG. 5B illustrates the LAA Scell operation case where the eNB is unableto transmit packets 506 via the LAA Scell before the end of the activetime 514, due to the failure of CCA on the Scell carrier. The eNB canconservatively setup a long DRX On-Duration 508, but this reduces theDRX opportunity and can reduce the power saving benefits of DRX.

Described below are several embodiments for improving DRX handling inLTE license assisted access operation.

A first embodiment generally involves extending the DRX active timebased upon a CCA failure. On the LAA carrier, the eNB is required toperform a CCA before transmitting a downlink signal (e.g., (E)PDCCH,PDSCH). If the CCA indicates that there is activity on the channel(i.e., channel is occupied by another device), the eNB skips thetransmission.

Referring now to FIG. 6, in one example the UE performs CCA (preferablyin the same time period as the CCA performed by the eNB) during, or justbefore, each subframe during the initial active time corresponding tothe DRX On-Duration 608, during which time the UE is monitoring for(E)PDCCH. If the CCA indicates that the channel is busy (e.g., CCA 602),the UE extends the active time 612 by one subframe. Correspondingly, ifthe CCA performed by the eNB (e.g., CCA 604) indicates that the channelis busy, the eNB assumes that the UE has extended its active time 612 byone subframe. Alternatively, instead of one subframe, the active timeextension can be a predefined ‘n’ number of subframes. Furthermore, theextension can be performed based on the CCA indicating that the channelis busy during one or more of the subframes close to the end of theOn-Duration (i.e., the “initial active time”) such as CCA 606. After asuccessful CCA (not shown), the packets 506 may then be transmitted fromthe Scell to the UE, shown here as transmission 614. While suchtransmission 614 is shown as occurring entirely within the active timeextension 610, such transmission can occur at any time during the activetime, including during later portions of the initial active time, orduring the extended active time subsequent to the initial active time.

The extension of the active time may apply to (a) just the LAA carrierand possibly the carrier carrying the corresponding PUCCH (i.e., PUCCHassociated with the downlink LAA carrier for the UE), or (b) it mayapply to all carriers. The CCA procedure has to be performed (at boththe UE and the eNB) prior to the subframe in which the eNB expects totransmit or at the start of the subframe in which the eNB expects totransmit.

It should be noted that, although described above in the context ofdownlink transmissions from the eNB to the UE, the technique is alsouseful for uplink transmissions from the UE to the eNB.

When CCA is performed independently at both the UE and the LAA eNB, itis possible that one of the CCA procedures succeeds and the other fails.If the CCA at the eNB succeeds (e.g., CCA 604) and the CCA at the UEfails (i.e., there is a node that is visible to the UE but hidden to theeNB), the UE may apply an active time extension, but the eNB does notextend its active time, and may only attempt a transmission to the UEwithin the initial active time (i.e., during the DRX On-Duration 608).This transmission will nonetheless occur within the respective activetimes of both the UE and eNB, and thus, the transmission will beaccomplished before the UE goes into DRX.

Conversely, if the CCA at the eNB fails and the CCA at the UE succeeds(i.e., there is a node that is visible to the eNB but hidden to the UE),the eNB may apply an active time extension, but the UE does not extendits active time since its CCA succeeded. However, the eNB assumes thatthe UE has extended its active time and may attempt a transmission tothe UE. If the UE has already gone into DRX, this transmission willfail.

In order to avoid the above problem, different energy detectionthresholds may be used for the CCA procedure at the eNB relative to theCCA procedure at the UE. That is, a more aggressive threshold (a lowerthreshold) may be used by the UE for its CCA procedure. The use of alower threshold at the UE makes it unlikely that there is a CCA successat the UE when there is a CCA failure at the eNB. The threshold used bythe UE can be selected by the eNB and signaled to the UE. Such selectionmay be based upon, for example, the estimated distance between the UEand the eNB (e.g., using signal measurements such as RSRP, etc.).Alternatively, the eNB can use a more relaxed threshold (a higherthreshold) than a default threshold used by the UE.

Referring now to FIG. 7, another embodiment generally involves extendingthe DRX active time based upon an indication on another carrier. In oneexample, the eNB performs CCA at the LAA Scell (e.g., CCA 702 during theinitial active time 708) prior to transmitting signals to the UE. If theeNB does not find adequate number of subframes in which it can transmitto the UE on the LAA Scell (due to the CCA procedure indicating that thecarrier is occupied), the eNB transmits to the UE via a cell on alicensed carrier (e.g., Pcell) an order 704 to extend the active time onthe LAA Scell. The order (i.e., command; message) may include the numberof subframes by which the active time 712 should be extended. The UEreceives the order to extend the active time (labeled 706), and extendsthe active time 712 accordingly. Alternatively, the eNB may transmit theorder to the UE to extend the active time via the LAA Scell itself at atime when the carrier is not occupied.

As in the previous approach, the extension 710 of the active time 712may apply to (a) just the LAA carrier and possibly the carrier carryingthe corresponding PUCCH (i.e., PUCCH associated with the downlink LAAcarrier for the UE), or (b) it may apply to all carriers. Althoughdescribed above in the context of downlink transmissions from the eNB tothe UE, the technique is also useful for uplink transmissions from theUE to the eNB.

To be able to transmit the ‘DRX Active Time Extension Order’ via thePcell, the entity controlling the Pcell has to be made aware of the CCAfailures on the LAA Scell. One of the expected modes of operation of LAAconsists of the Pcell being operated by a macro eNB and the LAA Scellbeing operated by a low power node (e.g., an indoor transmission pointor a small cell). In such a case, transmitting the ‘DRX Active TimeExtension Order’ as shown requires signaling between the node operatingthe LAA Scell (referred to as LAA Scell eNB) and the macro celloperating the Pcell. An example of such signaling may be described asfollows:

-   -   1. The LAA Scell eNB performs CCA at the LAA Scell prior to        transmitting signals to the UE.    -   2. If the LAA Scell eNB does not find adequate number of        subframes in which it can transmit to the UE on the LAA Scell        (due to CCA being unsuccessful). The LAA Scell eNB then        transmits an indication to the macro eNB controlling the Pcell        that an active time extension is needed and includes a number of        subframes of extension.    -   3. The macro eNB receives the indication from the LAA Scell eNB        and transmits to the UE a ‘DRX active time extension order’        including the number of subframes of extension.    -   4. The UE receives the order and extends the active time        accordingly.

The above scheme where information related to the need for active timeextension is exchanged between the eNBs is preferred over a scheme wherethe LAA Scell eNB sends un-transmitted packets to the macro eNB, as thatrequires a higher capacity backhaul communication link.

In some embodiments, the active time extension can be handleddifferently for licensed and unlicensed carriers. A Cell Radio NetworkTemporary Identifier (CRNTI) is a unique identifier of the UE whenconnected to an eNB. In one example, if a control channel (e.g., PDCCH)with CRNTI for the UE is received by that UE from a cell on a licensedcarrier (Pcell or Scell) such a command may serve to extend the activetime for all the configured cells (for that UE) on licensed carriers.

In some embodiments, if a UE receives a data packet or downlink controlinformation (DCI) on a control channel from the eNB (e.g., a PDCCH witha CRNTI) on an LAA Scell, the active time is extended for that LAA Scellbut not for the other carriers.

In some embodiments, the eNB signals an indication of a start oftransmission burst (e.g., preamble transmission following successfulCCA) with transmission burst configuration parameters such as thetransmission burst duration (N_Tx_Burst) and/or transmission burstsubframe configuration. Based on the received transmission burstconfiguration signaling, if a UE receives a data packet or a DCI on acontrol channel from the eNB (e.g., a PDCCH with a CRNTI) on an LAAScell towards the end of the transmission burst (e.g., in last Xsubframes) (and possibly towards the end of the DRX ON duration for theUE), the active time is extended for that LAA Scell, to account for thediscontinuous transmission regulatory requirements on the LAA Scell,idle period, and the need for the eNB to perform LBT before reinitiatingtransmission. The amount of active time extension (i.e., number ofsubframes by which the active time should be extended) may be indicatedin the transmission burst configuration signaling in the preambletransmission.

In some embodiments, the DRX active time extension order is sent on theLAA Scell if the eNB estimates that an inadequate number of subframesare available in which it can transmit to the UE on the LAA Scell. Inone alternative, the DRX active time extension order indication may besignaled in a DCI on a control channel that does not include resourceassignment for the UE. The DCI may include DRX active time extensionindication for a group of UEs (e.g., DCI on PDCCH with DRX-RNTI) withthe DCI comprising an indication for each UE in the group of UEs. Theindication may specify whether active time extension is to be appliedfor the UE and the amount of active time extension for the UE. The UE isconfigured by higher layer on the position (e.g., bits) within the DCIthat corresponds to DRX active time extension indication for that UE. Inanother alternative, the DRX active time extension order indication maybe signaled in a DCI on a control channel together with resourceassignment message for a data packet for a UE. This may be achieved byusing one or more bits or states in the DCI for signaling theindication.

In some embodiments, if the UE's CCA on the LAA Scell is not successfulduring the DRX On-Duration, the active time is extended for the LAAScell (but not for the other carriers).

As a further modification of the above procedures, the active time ofall LAA Scells can be extended if the active time on any one LAA Scellis extended.

While some of the description (and corresponding figures) of techniquespresented above may be described in the context of a UE device, thetechniques can also be used when the wireless communication device is aninfrastructure node (i.e., base station) such as a Wi-Fi access point,an eNB or a small cell. For example, the wireless communication devicecan be an infrastructure node that supports Wi-Fi operation on one ormore carriers and LTE LAA operation on one or more carriers. Thewireless communication device can also be an infrastructure node thatsupports LTE LAA operation on two or more carriers. Moreover, variousDRX techniques described herein may also be utilized with other wirelesstechnologies that do not necessarily utilize separate control channelsfor resource allocation. For example, Wi-Fi transmissions includeinformation in a packet header to identify the intended recipient.

The various techniques described above are contemplated to be used aloneor in combination. In addition, while methods and techniques aregenerally described above, various wireless communication devices (suchas, for example, UE's and eNB's) and systems that are operable toperform such methods and techniques are also contemplated.

It should be understood that the drawings and detailed descriptionherein are to be regarded in an illustrative rather than a restrictivemanner, and are not intended to be limiting to the particular forms andexamples disclosed. On the contrary, included are any furthermodifications, changes, rearrangements, substitutions, alternatives,design choices, and embodiments apparent to those of ordinary skill inthe art, without departing from the scope of the invention as defined bythe claims in this application or in any application claiming priorityto this application. Thus, it is intended that such claims beinterpreted to embrace all such further modifications, changes,rearrangements, substitutions, alternatives, design choices, andembodiments.

What is claimed is:
 1. A method in a mobile device, the methodcomprising: receiving, by the mobile device, from a first cell operatingon an unlicensed carrier, an indication of an energy detection thresholdfor a clear channel assessment (CCA), where the received indication ofthe energy detection threshold is an indication of an energy detectionthreshold specific to the mobile device; determining whether theunlicensed carrier is occupied based upon the CCA and the receivedenergy detection threshold; and communicating a data packet between themobile device and the first cell when the unlicensed carrier is nototherwise occupied, wherein the CCA comprises a user equipment CCA, andwherein the received energy detection threshold is a lower thresholdthan a network entity threshold utilized by a network entity of thefirst cell to perform a corresponding network entity CCA atsubstantially the same time as determining whether the unlicensedcarrier is occupied based on the user equipment CCA.
 2. The methodaccording to claim 1, further comprising transmitting a signalmeasurement by the mobile device, wherein the energy detection thresholdis based on the transmitted signal measurement.
 3. The method accordingto claim 1, further comprising: monitoring, in the mobile device, for asignal addressed to the mobile device from the first cell during anactive time having an initial duration equal to an initial active time;receiving, by the mobile device, on a control channel, downlink controlinformation (DCI) indicating a command to extend the active time;extending, in the mobile device, the active time in response to thereceiving the command to extend the active time; and whereincommunicating comprises communicating the data packet between the mobiledevice and the first cell during the extended active time.
 4. The methodaccording to claim 3, wherein the DCI further comprises a resourceassignment for a transmission of a data channel to the mobile device;and wherein communicating the data packet between the mobile device andthe first cell during the extended active time comprises receiving, bythe mobile device, the data packet from the data channel.
 5. The methodaccording to claim 3, wherein the command to extend the active time isindicated in the DCI by at least one selected from at least one bit inand at least one state indicated by the DCI.
 6. The method according toclaim 3, wherein the DCI is a group-common DCI with cyclic redundancycheck (CRC) scrambled with a Discontinuous Reception Radio NetworkTemporary Identifier (DRX-RNTI), where the group-common DCI is a DCI fora group of mobile devices; and wherein the method comprises extending,in the mobile device, the active time in response to the receiving thecommand to extend the active time in the group-common DCI.
 7. The methodaccording to claim 6, further comprising: receiving, by the mobiledevice, a higher layer configuration message indicating at least one bitposition within the group-common DCI that corresponds to the command toextend the active time for the mobile device; and wherein extending theactive time comprises extending the active time in response to thereceiving the command to extend the active time in the indicated atleast one bit position in the group-common DCI.
 8. The method accordingto claim 3, wherein receiving the DCI comprises receiving the DCIindicating the command to extend the active time based upon adetermination at the first cell that the unlicensed carrier is occupied.9. The method according to claim 3, wherein the command to extend theactive time indicates whether active time extension is to be applied forthe mobile device and an amount of active time extension, and whereinextending the active time comprises extending the active time by theindicated amount of active time extension in response to determining theactive time extension is to be applied based on the received command toextend the active time in the DCI.
 10. The method according to claim 3,wherein the command to extend the active time is received from a secondcell operating on a licensed carrier.
 11. The method according to claim3, wherein the extended active time is applied to the operation with thefirst cell on the unlicensed carrier and to a second cell operating on alicensed carrier carrying a corresponding Physical Uplink ControlChannel (PUCCH) associated with a downlink of the first cell on the onthe unlicensed carrier.
 12. The method according to claim 3, furthercomprising further extending, in the mobile device, the extended activetime in response to a determination that the unlicensed carrier isoccupied during at least a portion of the extended active timesubsequent to the initial active time.
 13. The method according to claim1, wherein the extended active time is applied to operation with allconfigured cells for the mobile device.
 14. The method according toclaim 1, wherein communicating the data packet between the mobile deviceand the first cell comprises: receiving, from the first cell, a controlchannel indicating resources for transmission of the data packet by themobile device; and transmitting the data packet using the indicatedresources.
 15. An apparatus comprising: a transceiver that receives froma first cell operating on an unlicensed carrier, an indication of anenergy detection threshold for a clear channel assessment (CCA), wherethe received indication of the energy detection threshold is anindication of an energy detection threshold specific to the apparatus;and a controller coupled to the transceiver, where the controllerdetermines whether the unlicensed carrier is occupied based upon the CCAand the received energy detection threshold, wherein the transceivercommunicates a data packet between the apparatus and the first cell whenthe unlicensed carrier is not otherwise occupied, wherein the CCAcomprises a user equipment CCA, and wherein the received energydetection threshold is a lower threshold than a network entity thresholdutilized by a network entity of the first cell to perform acorresponding network entity CCA at substantially the same time thecontroller determines whether the unlicensed carrier is occupied basedon the user equipment CCA.
 16. The apparatus according to claim 15,wherein the transceiver transmits a signal measurement, wherein theenergy detection threshold is based on the transmitted signalmeasurement.
 17. The apparatus according to claim 15, wherein thecontroller monitors for a signal addressed to the apparatus from thefirst cell during an active time having an initial duration equal to aninitial active time, wherein the transceiver receives, on a controlchannel, downlink control information (DCI) indicating a command toextend the active time, wherein the controller extends the active timein response to the receiving the command to extend the active time, andwherein the transceiver communicates the data packet between theapparatus and the first cell during the extended active time.
 18. Theapparatus according to claim 17, wherein the DCI further comprises aresource assignment for a transmission of a data channel to theapparatus; and wherein the transceiver communicates the data packetbetween the apparatus and the first cell during the extended active timeby receiving the data packet from the data channel.
 19. The apparatusaccording to claim 18, wherein the command to extend the active time isindicated in the DCI by at least one selected from at least one bit inand at least one state indicated by the DCI.
 20. The apparatus accordingto claim 17, wherein the DCI is a group-common DCI with cyclicredundancy check (CRC) scrambled with a Discontinuous Reception RadioNetwork Temporary Identifier (DRX-RNTI), where the group-common DCI is aDCI for a group of mobile devices; and wherein the controller extendsthe active time in response to the receiving the command to extend theactive time in the group-common DCI.
 21. The apparatus according toclaim 20, wherein the transceiver receives a higher layer configurationmessage indicating at least one bit position within the group-common DCIthat corresponds to the command to extend the active time for theapparatus, and wherein the controller extends the active time byextending the active time in response to the receiving the command toextend the active time in the indicated at least one bit position in thegroup-common DCI.
 22. The apparatus according to claim 17, wherein thetransceiver receives the DCI by receiving the DCI indicating the commandto extend the active time based upon a determination at the first cellthat the unlicensed carrier is occupied.
 23. The apparatus according toclaim 17, wherein the command to extend the active time indicateswhether active time extension is to be applied for the apparatus and anamount of active time extension, and wherein the controller extends theactive time by extending the active time by the indicated amount ofactive time extension in response to determining the active timeextension is to be applied based on the received command to extend theactive time in the DCI.
 24. The apparatus according to claim 15, whereincontroller applies the extended active time to operation with allconfigured cells for the apparatus.
 25. The apparatus according to claim15, wherein the transceiver communicates the data packet between theapparatus and the first cell by: receiving, from the first cell, acontrol channel indicating resources for transmission of the data packetby the apparatus; and transmitting the data packet using the indicatedresources.